The ratio of the magnetic field at the centre of a current-carrying circular coil to its magnetic moment is x . If the current and radius each of them are made three times, the new ratio will become

Question

The ratio of the magnetic field at the centre of a current-carrying circular coil to its magnetic moment is x . If the current and radius each of them are made three times, the new ratio will become, 3 x, 9 x, x 9, x 27

MARKS App · Accepted Answer

The magnetic field, B = μ 0 I 2 R ∴ Magnetic moment, μ = I A B μ = μ 0 I 2 R Iπ R 2 = μ 0 2 π R 3 ∝ 1 R 3 if R and I are made three times, new B ' μ = 1 27 B μ = x 27

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